CAIE A-Level Chemistry 24.1.1 Products of Electrolysis

Practise predicting substances liberated at each electrode from electrolyte state, concentration and redox data.

Exam points

for a molten electrolyte, discharge only its constituent ions and identify reduction at the cathode
for aqueous solutions, compare competing water/H+ and solute half-reactions using electrode potentials
account for concentration where relevant and write the selected half-equation with states and electrons

[Maximum number: 1]

Potassium iodide, KI, is used as a reagent in both inorganic and organic chemistry.

A student electrolyses a solution of KI(aq) for 8 minutes using a direct current. The half-equation for the reaction that occurs at the anode is given.

2 \mathrm{I}^{-}(\mathrm{aq}) \rightarrow \mathrm{I}_{2}(\mathrm{aq})+2 \mathrm{e}^{-}

Write a half-equation for the reaction that occurs at the cathode.

Include state symbols.

$2 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_{2}(\mathrm{~g})$ state symbols required

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24.1.1—The identities of substances liberated during question 1